Taught By

Virginie BOUTUEIL

Researcher

Émeric FORTIN

Head of the Master in Transport and Sustainable Development

Transcript

Electric Vehicles and Mobility More on method The Technical and Economic Processes Leading to an Equilibrium Between Supply and Demand on Electric Grids The European electric grid is synchronous around 50 Hz and stretches from Spain to Tunisia. So the equilibrium is guaranteed at the European scale and beyond. The equilibrium is nationwide first, but the capacities at the borders determine the possibilities of extraterritorial adjustments. Whoever manages the high-voltage electricity transmission grid is responsible for the balance between production and consumption and creates models to forecast demand one year ahead, then 7 days ahead, and then 24 hours ahead. All available parameters can be taken into account, is it a working day, the temperature, the cloud cover, specific events such as football matches, which lead to a demand peak during commercial breaks. The production orders are thus given on the day before to the power plants so they can follow the forecast demand curve. Power plants are set in motion based on their price for a kilowatt-hour. This is the merit order. The price of kilowatt-hour for every half hour is that of the last plant called upon and all will be paid at this price. Then, we reach an instantaneous equilibrium thanks to some of the existing leeway. Demand erasing, for instance. One actor, such as an industry, agrees to no longer be supplied by the grid and switches to an internal energy production source. Hydroelectric production is the only one capable of producing almost instantaneously. The kinetic energy stored in the plant's rotor alternator makes up a stock of low energy which allows the electric systems to absorb the disequilibrium between the mechanical power injected and the electric power extracted by the loads. The transmission grid manager may also call upon primary reserves to ensure the equilibrium and avoid any variations in frequencies. The apparition of solar and wind-powered intermittent generators compels operators to further anticipate when to start additional generators to recreate or increase reserves. It is not easy for the manager, especially since renewable sources usually take priority when they produce electricity. When they are deployed, there is more need for storage. Electric vehicles and their batteries may be an answer to this issue. Installing a fast-charging network also makes it harder to reach an equilibrium as it may strongly call upon the grid. These actors thus favor slow charging, which may even out electricity production by increasing it at night when demand is low, as with hot water tanks. In the future, the deployment of smart electric grids will allow us to act more directly on consumption. New incentive mechanisms will allow for more flexibility for the user as we will be able to start or shed the load at the most suitable time for the grid. This regulation will be associated with local storage in which electric vehicle fleets will play a central part. The vehicle-to-grid process, VTG, is well-suited for the frequency market as technically, batteries associated with power electronics allow for immediate reaction and supply capacity rather than energy. There are obstacles to the implementation. In terms of legislation and regulations, there are not yet any laws regarding decentralized storage. Then, the systems costs are still high, which limits the economic model. And today, these services are not yet paid for. So it is hard for an outside operator to take part in the system services. Eventually, we will be able to supply new services to the users. An aggregator must be able to collect date reasonably and communicate with the vehicles and the market manager.

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